1. Field of the Invention
This invention relates to a process for producing serine.
2. DESCRIPTION OF THE PRIOR ART
Serine is a kind of an alpha-amino acid. L-serine is used as a component of a parenteral solution, and D-serine is useful as a material for cycloserine, an antibiotic. Serine is also useful as a material for the production by an enzymatic process of L-tryptophan which is expected to gain future acceptance as a feed additive.
One conventional process for production of DL-serine from aziridine-2-carboxylic acid comprises heating in 15% sulfuric acid lithium aziridine-2-carboxylate synthesized by hydrolysis of ethyl aziridine-2-carboxylate in the presence of lithium hydroxide [K. D. Gundermann, Chem. Ber., 93, 1639 (1960)]. This process, however, requires the use of a large excess (about 12 moles) of sulfuric acid relative to the starting lithium aziridine-2-carboxylate. In order to separate the resulting serine from the reaction mixture after the reaction, the excess sulfuric acid should be neutralized with calcium hydroxide or barium hydroxide to precipitate it as calcium sulfate or barium sulfate, followed by separating the salt by filtration. The process steps, therefore, become complex and the reactor volume is large. If an anion having higher nucleophilic reactivity than water, such as a halogen ion, is present in the hydrolysis of aziridine-2-carboxylic acid in sulfuric acid, a compound having such an ion added thereto forms as a by-product to decrease the yield of DL-serine.
It is an object of this invention therefore to provide a process for producing DL-serine from aziridine-2-carboxylic acid or its alkali or alkaline earth metal salt which can be produced relatively easily.
The salt of aziridine-2-carboxylate can be easily obtained by heating an aqueous solution of an alpha-halogeno-beta-aminopropionitrile or its mineral acid salt, which can be easily produced by the reaction of an alpha, beta-dihalogenopropionitrile or an alpha-halogenoacrylonitrile with ammonia, together with an alkali or alkaline earth metal hydroxide.